Roller device, fixing device, and image forming apparatus

ABSTRACT

The cleaning member is disposed to be opposite to the first roller with the second roller being provided therebetween. Compared to a case when the second roller is placed at a first position on a side of the first roller, if the second roller is placed at a second position on a side of the cleaning roller, a pressure between the second roller and the first roller becomes smaller, and a pressure between the second roller and the cleaning member becomes larger.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a roller device, a fixing device, andan image forming apparatus such as a copying machine, a multifunctionmachine, a printer apparatus, or a facsimile apparatus.

2. Description of the Background Art

When a roller device that includes a first roller and a second rollerswingable to change the pressure on the first roller is included in animage forming apparatus, for example, the roller device is used for afixing device in which the first roller is a fixing roller and thesecond roller is a pressure roller.

In such a roller device, a surface of the second roller is usuallycontaminated by foreign matter such as paper dust and toner. For thisreason, the roller device usually includes a cleaning member thatcontacts the second roller to clean the second roller.

In a conventional roller device including such a cleaning member, thecleaning member is always made to press-contact the second roller with aconstant contact pressure. Consequently, if the surface of the secondroller is not contaminated or less contaminated, the contact pressure ofthe cleaning member on the second roller is always constant and the lifeof the cleaning member is reduced accordingly.

Regarding this point, Japanese Patent Laying-Open No. 2003-167456describes a configuration in which a tension roller (the first roller)and a backup roller (the second roller) are moved to be close to eachother for the purpose of changing the contact pressure of a web (thecleaning member) disposed between the tension roller and the backuproller on the backup roller (see FIG. 4 in Japanese Patent Laying-OpenNo. 2003-167456). In addition, Japanese Patent Laying-Open No.2013-50662 describes a configuration in which a web sheet is moved awayfrom a pressure roller (a second roller) in response to the pressureroller moving away from a fixing roller (a first roller) (see FIGS. 2and 3 in Japanese Patent Laying-Open No. 2013-50662).

SUMMARY OF THE INVENTION

In the configurations described in Patent Laying-Open Nos. 2003-167456and 2013-50662, however, when a contact-pressure release operation isperformed to release the contact pressure of a second roller on a firstroller, a cleaning member cannot perform a cleaning operation.

The present invention has been achieved in view of the above problems,and an object of the invention is to provide a roller device thatincludes a first roller, a second roller swingable to change thepressure on the first roller, and a cleaning member which contacts thesecond roller to clean the second roller, that can improve the life ofthe cleaning member, and that enables the cleaning member to perform acleaning operation when the second roller performs a contact-pressurerelease operation on the first roller and to provide a fixing device andan image forming apparatus.

To solve the problems, the present invention provides a roller device, afixing device, and an image forming apparatus as follows.

(1) Roller Device

A roller device according to the present invention includes a firstroller, a second roller that is swingable to change a pressure on thefirst roller, and a cleaning member that contacts the second roller toclean the second roller. The cleaning member is disposed to be oppositeto the first roller with the second roller being provided between thecleaning member and the first member. When the second roller is placedat a first position on a side of the first roller, a pressure betweenthe second roller and the first roller is a first roller pressure and apressure between the second roller and the cleaning member is a firstcleaning pressure. When the second roller is placed at a second positionon a side of the cleaning roller, a pressure between the second rollerand the first roller is a second roller pressure less than the firstroller pressure, and a pressure between the second roller and thecleaning member is a second cleaning pressure larger than the firstcleaning pressure.

(2) Fixing Device

A fixing device includes the roller device according to the presentinvention. The first roller is a fixing roller and the second roller isa pressure roller.

(3) Image Forming Apparatus

An image forming apparatus includes the roller device according to thepresent invention or the fixing device according to the presentinvention.

According to the present invention, the life of the cleaning member canbe improved and when a contact-pressure release operation is performedto release the contact pressure of the second roller on first roller,the cleaning member can perform a cleaning operation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view of an image forming apparatusaccording to the present embodiment.

FIG. 2 is a perspective view of a schematic configuration of a fixingdevice shown in FIG. 1, as viewed from diagonally upper right on a frontside.

FIG. 3 is a perspective view of the schematic configuration of thefixing device shown in FIG. 1, as viewed from diagonally upper left onthe front side.

FIG. 4 is a perspective view of a press-contact unit in the fixingdevice shown in FIG. 1, as viewed from diagonally upper left on thefront side.

FIG. 5 is a perspective view of a cleaning unit as viewed fromdiagonally upper left on the front side.

FIG. 6 is a perspective view of the cleaning unit as viewed fromdiagonally upper right on the front side.

FIG. 7 is an exploded perspective view of the cleaning unit.

FIG. 8 is a longitudinal cross-sectional view of the fixing device,showing a state where a pressure roller is placed at a first position.

FIG. 9 is a longitudinal cross-sectional view of the fixing device,showing a state where the pressure roller is placed at a secondposition.

FIG. 10 is a system block diagram of a schematic configuration of acontrol system in the image forming apparatus according to the presentembodiment.

FIG. 11 is a timing chart of an example of a drive operation of thefixing device.

FIG. 12 is a timing chart of another example of the drive operation ofthe fixing device.

FIG. 13 is a timing chart of yet another example of the drive operationof the fixing device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below withreference to the drawings. In the following description, the samecomponents will be designated by the same reference numerals and,further, have the same names and the same functions. Consequently, thesecomponents will not be repeatedly described in detail.

[Overall Configuration of Image Forming Apparatus]

FIG. 1 is a schematic cross-sectional view of an image forming apparatus100 according to the present embodiment. The image forming apparatus 100according to the present embodiment is a color image forming apparatusthat forms a monochrome or multicolor image on a sheet P such as arecording sheet (specifically, a recording sheet) based on image dataread by an image reader 90 or image data externally transmitted. Theimage forming apparatus 100 may be a monochrome image forming apparatus.Alternatively, the image forming apparatus 100 may be other color imageforming apparatuses.

The image forming apparatus 100 includes a document feeder 108 and animage forming apparatus main body 110. The image forming apparatus mainbody 110 includes an image forming part 102 and a sheet transportingsystem 103.

The image forming part 102 includes an optical scanner 1, a plurality ofdevelopment devices 2, a plurality of photosensitive drums 3 functioningas an electrostatic latent image carrier, a plurality of cleaningdevices 4, a plurality of charging devices 5, an intermediate transferbelt device 6, a plurality of toner cartridge devices 21, and a fixingdevice 7. The sheet transporting system 103 includes a paper feed tray81, a manual paper feed tray 82, and a discharge tray 15.

A document table 92 composed of a transparent glass, on which a document(not shown) is placed, is disposed on the image forming apparatus mainbody 110. The image reader 90 for reading images of the document isdisposed under the document table 92. The document feeder 108 isdisposed on the document table 92. An image of the document read by theimage reader 90 is transmitted as image data to the image formingapparatus main body 110. An image formed based on the image data in theimage forming apparatus main body 110 is recorded on a sheet P.

Image data handled by the image forming apparatus 100 is applicable tocolor images using a plurality of colors (in this example, black (K),cyan (C), magenta (M), and yellow (Y)). Consequently, the developmentdevice 2, the photosensitive drum 3, the cleaning device 4, the chargingdevice 5, and the toner cartridge device 21 are respectively provided inplural (in this example, four for black, cyan, magenta, and yellow) soas to form a plurality types (in this example, four types of) images ofthe respective colors. In this way, a plurality of (in this example,four) image stations are configured.

When the image forming apparatus 100 forms images, a sheet P is suppliedfrom the paper feed tray 81 or the manual paper feed tray 82 andtransported to a registration roller 13 by a first transportation roller12 a disposed along a sheet transportation path S. Next, the sheet P istransported by a transfer roller 10 at a timing of registering tonerimages on an intermediate transfer belt 61 circulating in a circulationdirection V in the intermediate transfer belt device 6 on the sheet P,so that the toner images are transferred to the sheet P. The sheet Pthen passes through a fixing roller 71 and a pressure roller 72 in thefixing device 7 for the purpose of thermally melting and fixing unfixedtoner on the sheet P, and further passes through a second transportationroller 12 b and a discharge roller 31 to be discharged on the dischargetray 15.

[Fixing Device]

The fixing device 7 is a fixing device with a belt fixing system. In thefixing device 7, a fixing belt 74 is entrained about a plurality ofrollers (in this example, the fixing roller 71, a heating roller 73, anda tension roller 76). The fixing belt 74 transmits heat from the heatingroller 73 to the fixing roller 71. The fixing device 7 is configuredthat the pressure roller 72 is pressed against the fixing roller 71 viathe fixing belt 74.

In addition, the fixing belt 74 is heated by a heat source 73 c disposedinside of the heating roller 73. The fixing belt 74 is configured tokeep a predetermined fixing temperature based on a signal from atemperature detector 77. The fixing belt 74 thermally fixes multicolortoner images transferred to the sheet P on the sheet P with the pressureroller 72. The multicolor toner images thus melt, mix, and press-contactthe sheet P to be thermally fixed on the sheet P. The temperaturedetector 77 is a temperature sensor that detects the surface temperatureof the fixing belt 74 in a contact or noncontact manner, such as athermistor.

Next, an example of using the roller device 200 according to the presentembodiment for the fixing device 7 with a belt fixing system isdescribed below.

FIG. 2 is a perspective view of a schematic configuration of the fixingdevice 7 shown in FIG. 1, as viewed from diagonally upper right on thefront side. FIG. 3 is a perspective view of the schematic configurationof the fixing device 7 shown in FIG. 1, as viewed from diagonally upperleft on the front side. FIG. 4 is a perspective view of a press-contactunit 220 in the fixing device 7 shown in FIG. 1, as viewed fromdiagonally upper left on the front side. FIG. 5 is a perspective view ofa cleaning unit 230 as viewed from diagonally upper left on the frontside. FIG. 6 is a perspective view of the cleaning unit 230 as viewedfrom diagonally upper right on the front side. FIG. 7 is an explodedperspective view of the cleaning unit 230. FIGS. 8 and 9 arelongitudinal cross-sectional views of the fixing device 7. FIG. 8 showsa state where the pressure roller 72 is placed at a first position P1and FIG. 9 shows a state where the pressure roller 72 is placed at asecond position P2.

In the present embodiment, the fixing device 7 includes a first roller(in this example, the fixing roller 71), a second roller (in thisexample, the pressure roller 72), and a cleaning member (in thisexample, a cleaning roller 75). The pressure roller 72 can swing tochange the pressure on the fixing roller 71. The cleaning roller 75contacts the pressure roller 72 to clean the pressure roller 72. Thecleaning roller 75 is disposed to be opposite to the fixing roller 71with the pressure roller 72 being provided therebetween.

The fixing device 7 further includes the endless fixing belt 74, anurging member (specifically, a press-contact spring 78), and a swingmember 211. The fixing belt 74 is entrained about the fixing roller 71and the heating roller 73. The swing member 211 is supported by a mainbody of the fixing device 7 (specifically, a main body frame FL) to beswingable around a swing axis (a swing shaft Q1) along a direction of arotation axis of the pressure roller 72. The press-contact spring 78press-contacts the pressure roller 72 against the fixing roller 71 withthe fixing belt 74 being interposed between the pressure roller 72 andthe fixing roller 71. A fixing nip is thus formed between the fixingbelt 74 and the pressure roller 72. The press-contact spring 78 isconnected to the main frame FL at one end and to the swing member 211 atthe other end.

The fixing device 7 is constituted by a belt unit 210, a press-contactunit 220, and the cleaning unit 230.

The belt unit 210 includes the fixing roller 71, the heating roller 73,the fixing belt 74, and the tension roller 76. The fixing roller 71 isdisposed in the main frame FL in a manner that a rotation shaft 71 a isrotatable via a bearing 71 b. The fixing roller 71 includes an elasticlayer 71 c (see FIGS. 8 and 9). The fixing roller 71 is driven to rotatethrough a drive transmission unit (not shown) by rotation drive forcefrom a rotation drive part (not shown). The pressure roller 72 isdisposed in the swing member 211 in a manner that a rotation shaft 72 ais rotatable via a bearing 72 b. The pressure roller 72 includes anelastic layer 72 c (see FIGS. 8 and 9).

The heating roller 73 is disposed in the main body frame FL in a mannerthat a rotation shaft 73 a is rotatable via a bearing 73 b. The heatingroller 73 includes the heat source 73 c and heated by the heat source 73c. The fixing belt 74 can thus be heated through the heating roller 73.The tension roller 76 may be disposed outside the fixing belt 74.

The press-contact unit 220 functions as a unit that performspress-contact and pressure adjustments of the pressure roller 72 on thefixing roller 71, and press-contact release of the pressure roller 72from the fixing roller 71.

The press-contact unit 220 includes a drive device 221. The drive device221 swings the swing member 211 around the swing shaft Q1. The drivedevice 221 includes a rotation drive shaft 221 a, an eccentric cammember 221 b, a rotation drive part 221 c, and a drive transmissionmechanism 221 d.

Drive force is transmitted from the rotation drive part 221 c via thedrive transmission mechanism 221 d to the rotation drive shaft 221 a.The eccentric cam member 221 b is disposed on the rotation drive shaft221 a to contact a rotation member FL1 in the main body frame FL. Therotation drive part 221 c is configured by a drive motor. The drivetransmission mechanism 221 d is configured by a gear train. Theeccentric cam member 221 b can rotate by rotation drive forcetransmitted from the rotation drive part 221 c via the rotation driveshaft 221 a and the drive transmission mechanism 221 d. The eccentriccam member 221 b can thus swing the pressure roller 72 that is supportedby the swing member 211 against the press-contact spring 78 between thefirst position P1 about the swing shaft Q1 (see FIG. 8) and the secondposition P2 about the swing shaft Q1 (see FIG. 9). The first position P1is on a side of the fixing roller 71 and the second position P2 is on aside of the cleaning roller.

The cleaning unit 230 is disposed to be removable from the main bodyframe FL. The cleaning unit 230 is disposed to be opposite to the beltunit 210 with the pressure roller 72 being interposed therebetween. Thecleaning unit 230 includes a main body 231, a movable part 232, and anurging member (in this example, a press-contact spring 233).

The main body 231 supports the movable part 232 in a manner that themovable part 232 can move in a movement direction M along a radialdirection of the pressure roller 72 (in a horizontal direction) on theopposite side to the belt unit 210. Unit support parts 231 a arerespectively disposed at both end portions of the main body 231 in alongitudinal direction N. The longitudinal direction N is along an axialdirection of the cleaning roller 75. An engagement part 231 b is formedin each of the unit support parts 231 a (see FIG. 7). The engagementpart 231 b is recessed toward the pressure roller 72 in the movementdirection M. Roller support parts 232 a are respectively disposed atboth end portions of the movable part 232 in the longitudinal directionN. The cleaning roller 75 is supported by the roller support parts 232 ain a manner that the rotation shaft 75 a is rotatable about a rotationaxis. The rotation shaft 75 a is composed of metal materials including,for example, stainless, SUM, iron, nickel, and aluminum. A cleaningmember 75 b is formed on an outer peripheral part of the rotation shaft75 a. The cleaning member 75 b is composed of an elastic body, in thisexample, an elastic foam body (a sponge layer). The elastic foam body isnot particularly limited, and commonly used foam materials may be used.Examples of the elastic foam body include foam bodies using organicrubbers including polyurethane, isoprene rubber (IR), nitrile rubber(NBR), ethylene propylene diene rubber (FPDM) or foam bodies using atleast one of polyethylene, polyester resin, polypropylene, polyamide,polyurethane, and epoxy resin. The roller support part 232 a engageswith the engagement part 231 b of the unit support part 231 a so as tobe movable in the movement direction M. The press-contact spring 233urges the roller support part 232 a toward the pressure roller 72. Thepress-contact spring 233 is connected to the unit support part 231 a ina perpendicular direction Z (a vertical direction or a substantiallyvertical direction) perpendicular to the movement direction M and thelongitudinal direction N to cover a side of the roller support part 232a opposite to a side at which the pressure roller 72 is disposed.

The pressure roller 72 and the heating roller 73 are rotated in responseto rotation of the fixing roller 71. The cleaning roller 75 is rotatedin response to rotation of the pressure roller 72.

(Control Unit)

FIG. 10 is a system block diagram of a schematic configuration of acontrol system in the image forming apparatus 100 according to thepresent embodiment.

As shown in FIG. 10, the image forming apparatus 100 further includes acontrol unit 130. The control unit 130 includes a processing unit 131and a storage unit 132. The processing unit 131 is configured by amicrocomputer such as a CPU. The storage unit 132 includes a nonvolatilememory such as a ROM and a volatile memory such as a RAM. The controlunit 130 is configured to control operations of various constituentelements when the processing unit 131 loads a control program stored inadvance in a ROM of the storage unit 132 into a RAM of the storage unit132 and performs the program. The control unit 130 may be included inthe fixing device 7.

Detection of Position of Pressure Roller

The fixing device 7 further includes a position detector 240 (see FIGS.2 to 4 and FIG. 10). The position detector 240 includes a detected part241 and a detector 242. The detected part 241 is constituted by aneccentric cam member 241 a and an arm 241 b. The eccentric cam member241 a is disposed at one end portion of the rotation drive shaft 221 a.The arm 241 b is supported by the main body frame FL to be rotatableabout a rotation axis (a rotation shaft Q2) along the longitudinaldirection N. One end portion of the arm 241 b slide-contacts theeccentric cam member 241 a. The arm 241 b is rotated about the rotationshaft Q2 in response to rotation of the eccentric cam member 241 a. Thedetector 242 detects the other end portion of the arm 241 b by rotationof the arm 241 b about the rotation shaft Q2. The detector 242 is atransmissive optical sensor. The detector 242 is electrically connectedto an input system of the control unit 130. The control unit 130 candetect the home position (the original position) of the eccentric cammember 241 a and then the home position of the pressure roller 72. Therotation drive part 221 c is electrically connected to an output systemof the control unit 130. The control unit 130 can thus control anoperation of the rotation drive part 221 c.

Swing Operation of Pressure Roller

The control unit 130 outputs an operation signal indicating therotational position (the rotation angle) of the eccentric cam member 241a determined by using the home position (the original position) of theeccentric cam member 241 a as a reference to the rotation drive part 221c. The control unit 130 can rotate the eccentric cam member 241 a viathe rotation drive shaft 221 a by the rotation drive unit 221 c.Consequently, it is possible to perform press-contact and pressureadjustments of the pressure roller 72 on the fixing roller 71 andpress-contact release of the pressure roller 72 from the fixing roller71.

First Embodiment

In the present embodiment, when the pressure roller 72 is placed at thefirst position P1, the pressure between the pressure roller 72 and thefixing roller 71 is a first roller pressure. At this time, a cleaningoperation is performed in a state where the pressure between thepressure roller 72 and the cleaning roller 75 is a first cleaningpressure. Meanwhile, when the pressure roller 72 is placed at the secondposition P2, the pressure between the pressure roller 72 and the fixingroller 71 is a second roller pressure less than the first rollerpressure. At this time, the cleaning operation is performed in a statewhere the pressure between the pressure roller 72 and the cleaningroller 75 is a second cleaning pressure larger than the first cleaningpressure. Consequently, when the pressure roller 72 is placed at thefirst position P1, the pressure between the pressure roller 72 and thecleaning roller 75 is the first cleaning pressure less than the secondcleaning pressure. The life of the cleaning roller 75 can thus beimproved. In addition, even when the pressure roller 72 is placed at thesecond position P2, the cleaning roller 75 can perform the cleaningoperation. Consequently, if a contact-pressure release operation isperformed to release the pressure of the pressure roller 72 on thefixing roller 71, the cleaning roller 75 can perform the cleaningoperation.

As the contact pressure between the cleaning roller 75 and the pressureroller 72 is increased, the cleaning performance of the cleaning roller75 is improved. When the contact pressure between the cleaning roller 75and the pressure roller 72 is too large, however, foreign matter adheredto the cleaning roller 75 by the cleaning operation may return to thepressure roller 72. When the cleaning operation is performed during animage forming operation, the foreign matter may affect images.

Regarding this point, the image forming operation can be performed whenthe pressure roller 72 is placed at the first position P1 in the presentembodiment. The image forming operation can be performed when thecontact pressure between the cleaning roller 75 and the pressure roller72 is small. Consequently, when the cleaning operation is performedduring the image forming operation, it is possible to prevent theforeign matter adhered to the cleaning roller 75 by the cleaningoperation from returning to the pressure roller 72. It is thus possibleto prevent the foreign matter from affecting images. In addition, it maybe configured that the image forming operation is not performed when thepressure roller 72 is placed at the second position P2. Consequently,the image forming operation is not performed when the contact pressurebetween the cleaning roller 75 and the pressure roller 72 is large. Thecleaning performance of the cleaning roller 75 can thus be more improvedthan that during the image forming operation. If the foreign matteradhered to the cleaning roller 75 by the cleaning operation returns tothe pressure roller 72, the image forming operation is not performed andthus influence of the foreign matter on images is not particularlyproblematic.

Magnitude relationships between the first roller pressure, the secondroller pressure, the second cleaning pressure, and the first cleaningpressure are as follows.

The first roller pressure may be larger than the second cleaningpressure and the second cleaning pressure may be larger than the secondroller pressure. In this case, the second roller pressure may be largerthan the first cleaning pressure or may be equal to the first cleaningpressure (first roller pressure>second cleaning pressure>second rollerpressure>first cleaning pressure).

Alternatively, the first roller pressure may be larger than the secondcleaning pressure and the second cleaning pressure may be larger thanthe first cleaning pressure. In this case, the first cleaning pressuremay be larger than the second roller pressure (including a case where nopressure is applied) (first roller pressure>second cleaningpressure>first cleaning pressure>second roller pressure).

Alternatively, the first roller pressure may be larger than the secondcleaning pressure and the second cleaning pressure may be equal to thesecond roller pressure. In this case, the second roller pressure may belarger than the first cleaning pressure (first roller pressure>secondcleaning pressure=second roller pressure>first cleaning pressure).

Alternatively, the first roller pressure may be larger than the secondroller pressure and the second roller pressure may be larger than thesecond cleaning pressure. In this case, the second cleaning pressure maybe larger than the first cleaning pressure (first roller pressure>secondroller pressure>second cleaning pressure>first cleaning pressure).

The contact pressure between the cleaning roller 75 and the pressureroller 72 can be changed in the present embodiment. The contact pressurebetween the cleaning roller 75 and the pressure roller 72 can thus bechanged according to contamination on a surface of the pressure roller72. The degree to which the cleaning roller 75 cleans the pressureroller 72 can thus be adjusted. That is, when the surface of thepressure roller 72 is less contaminated, the contact pressure betweenthe cleaning roller 75 and the pressure roller 72 is less than that whenthe surface of the pressure roller 72 is contaminated. It is thuspossible to prevent a reduction in the life of the cleaning roller 75.Such an adjustment is preferably performed when the pressure roller 72is placed at the second position P2.

The cleaning roller 75 is urged toward the pressure roller 72 by thepress-contact spring 78 in the present embodiment. The contact pressurebetween the cleaning roller 75 and the pressure roller 72 can thus beincreased. It is thus possible to further improve the cleaningperformance of the cleaning roller 75.

The pressure roller 72 may be formed in a manner that its outer diameteris gradually increased from a center portion of the pressure roller 72in the longitudinal direction N toward an outer end portion thereof(formed in an inverted crown shape). In this case, when the outerdiameter of the cleaning roller 75 is constant or substantially constantin the longitudinal direction N, the contact pressure between thecleaning roller 75 and the pressure roller 72 is not uniform in thelongitudinal direction N. Consequently, the cleaning performance of thecleaning roller 75 may vary in the longitudinal direction N.

Regarding this point, when the pressure roller 72 is formed in aninverted crown shape, the cleaning roller 75 is formed in a manner thatits outer diameter is gradually reduced from a center portion of thecleaning roller 75 in the longitudinal direction N toward an outer endportion thereof (formed in a crown shape) according to the shape of thepressure roller 72. The contact pressure between the cleaning roller 75and the pressure roller 72 can thus be uniform in the longitudinaldirection N of the pressure roller 72. Consequently, the cleaningperformance of the cleaning roller 75 is constant or substantiallyconstant in the longitudinal direction N.

It is configured in the present embodiment that the pressure roller 72steplessly swings relative to the fixing roller 71 by a cam mechanism.The contact pressure between the cleaning roller 75 and the pressureroller 72 can thus be changed steplessly. The contact pressure betweenthe cleaning roller 75 and the pressure roller 72 can be steplesslychanged depending on contamination on the surface of the pressure roller72. The degree to which the cleaning roller 75 cleans the pressureroller 72 can be adjusted steplessly. In addition, the contact pressurebetween the pressure roller 72 and the fixing roller 71 (the fixing belt74) can be steplessly changed. The contact pressure between the pressureroller 72 and the fixing roller 71 can be steplessly changed dependingon the degree of toner fixing. In this example, the control unit 130 isconfigured to adjust the degree of cleaning and/or the degree of fixingthrough an input screen displayed on a display unit (not shown) in anoperation unit (not shown) in a simulation mode. On the input screen,values of the contact pressure between the cleaning roller 75 and thepressure roller 72 when the pressure roller 72 is placed at the secondposition P2 and/or values of the contact pressure between the pressureroller 72 and the fixing roller 71 when the pressure roller 72 is placedat the first position P1 can be input.

The fixing belt 74 is entrained about the fixing roller 71 in thepresent embodiment. In this manner, the configuration of the presentembodiment can be applied to a fixing device of a fixing belt type.

Second Embodiment

In the present embodiment, during an image forming operation, thecontrol unit 130 drives the fixing device 7 to rotate the fixing roller71 in the same direction as the rotation direction of the fixing roller71 during the image forming operation while the pressure roller 72 isplaced at the first position P1. The control unit 130 performs, for apredetermined first period T1, a first drive operation of driving thefixing device 7 to rotate the fixing roller 71 in the same direction asthe rotation direction of the fixing roller 71 during the image formingoperation while the pressure roller 72 is placed at the first positionP1. In addition, the control unit 130 performs, for a predeterminedsecond period T2, a second drive operation of driving the fixing device7 to rotate the fixing roller 71 in the same direction as the rotationdirection of the fixing roller 71 during the mage forming operationwhile the pressure roller 72 is placed at the second position P2. Thefirst drive operation is thus continuously shifted to the second driveoperation before or after the image forming operation.

FIG. 11 is a timing chart of an example of a drive operation of thefixing device 7. In an example of FIG. 11, the control unit 130 performsa first drive operation for a first period T1 (for example, for oneminute) immediately after an image forming operation and then performs asecond drive operation for a second period T2 (for example, for oneminute) immediately after the first drive operation. The image formingoperation can thus be smoothly shifted to the first drive operationwithout switching the position of the pressure roller 72.

FIG. 12 is a timing chart of another example of the drive operation ofthe fixing device 7. In an example of FIG. 12, in addition to theconfiguration shown in FIG. 11 or instead of that, the control unit 130performs a second drive operation for a second period T2 (for example,ten seconds) at the time of start-up of the image forming apparatus 100and then performs a first drive operation for a first period T1 (forexample, ten seconds) immediately after the second drive operation. Whenreceiving an instruction to perform an image forming operation, thecontrol unit 130 performs the image forming operation. The first driveoperation can thus be smoothly shifted to the image forming operationwithout switching the position of the pressure roller 72.

Third Embodiment

In the present embodiment, the control unit 130 performs a third driveoperation of driving the fixing device 7 to rotate the pressure roller72 in the opposite direction to the rotation direction of the pressureroller 72 during an image forming operation while the pressure roller 72is placed at the second position P2. The pressure roller 72 can thusrotate in the opposite direction to the rotation direction of thepressure roller 72 during the image forming operation. The cleaningperformance of the cleaning roller 75 can thus be further improved.

FIG. 13 is a timing chart of yet another example of the drive operationof the fixing device 7. In an example of FIG. 13, the control unit 130performs a first drive operation for a first period T1 (for example, forone minute) immediately after the image forming operation, then performsa second drive operation for a second period T2 (for example, for 50seconds) immediately after the first drive operation, and performs athird drive operation for a third period T3 (for example for tenseconds) immediately after the second drive operation. The pressureroller 72 can thus rotate in the opposite direction to the rotationdirection of the pressure roller 72 during the image forming operationwithout switching the position of the pressure roller 72. The cleaningperformance of the cleaning roller 75 can thus be further improved.

In the second drive operation shown in FIG. 11 and the second and thirddrive operations shown in FIG. 13, the fixing device 7 is driven in astate where heating of the heating roller 73 is stopped. The fixingroller 71, the pressure roller 72, the heating roller 73, the fixingbelt 74, and the like can thus be uniformly cooled.

Other Embodiments

While the cleaning member is a cleaning roller in the presentembodiment, the cleaning member may be a cleaning web or a cleaning pad.

While the roller device is used for a fixing device with a belt fixingsystem in the present embodiment, the roller device may be used for afixing device without a belt. In addition, while the roller device isused for a fixing device, the roller device may be used for atransportation device that transports sheets in an image formingapparatus.

The present invention is not limited to the embodiments described above,and may be implemented in other various forms. These embodiments areonly illustrative in all aspects, not restrictive. The scope of thepresent invention is defined by the appended claims and is notrestricted by the specification. Modifications and changes fallingwithin the equivalent scope of the claims are all included in the scopeof the present invention.

What is claimed is:
 1. A fixing device comprising: a first roller; asecond roller that is provided in contact with the first roller; acleaning member that is provided in contact with the second roller toclean the second roller; a driver that drives the second rollerswingingly relative to the first roller; and a controller that controlsthe driver, wherein the controller controls the driver to driveswingingly the second roller relative to the first roller so as tochange a pressure between the second roller and the first roller and apressure between the second roller and the cleaning member to apredetermined relationship in accordance with a position to which thesecond roller is driven swingingly, wherein the predeterminedrelationship according to the position to which the second roller isdriven swingingly in such that when the second roller is drivenswingingly to a first position on a side of the first roller, thepressure between the second roller and the first roller is a firstroller pressure and the pressure between the second roller and thecleaning member is a first cleaning pressure, and when the second rolleris driven swingingly to a second position on a side of the cleaningmember, the pressure between the second roller and the first roller is asecond roller pressure less than the first roller pressure, and thepressure between the second roller and the cleaning member is a secondcleaning pressure larger than the first cleaning pressure.
 2. The fixingdevice according to claim 1, further comprising a position detector thatdetects a position of the second roller, wherein the controller controlsthe driver in accordance with a detection result of the positiondetector, and the cleaning member is provided with being urged on thesecond roller.
 3. The fixing device according to claim 1, wherein thedriver is configured to drive the second roller to steplessly swingrelative to the first roller.
 4. The fixing device according to claim 1,wherein the first roller is a fixing roller and the second roller is apressure roller.
 5. The fixing device according to claim 4, wherein afixing belt is entrained about a fixing roller.
 6. The fixing deviceaccording to claim 1, wherein the driver is configured to drive thefirst roller to rotate, and the controller is configured to control thedriver to perform a first drive operation in a first period to rotatethe first roller in a same direction as a rotation direction in whichthe first roller is rotated during an image forming operation while thesecond roller is placed at the first position, and perform a seconddrive operation in a second period to rotate the first roller in thesame direction as the rotation direction in which the first roller isrotated during the image forming operation while the second roller isplaced at the second position.
 7. The fixing device according to claim6, wherein the controller performs the first drive operation after animage forming operation and performs the second drive operation afterthe first drive operation.
 8. The fixing device according to claim 7,wherein the controller further performs a third drive operation in athird period to rotate the second roller in a direction opposite to arotation direction in which the second roller is rotated during an imageforming operation while the second roller is placed at the secondposition.
 9. The fixing device according to claim 8, wherein thecontroller performs the third drive operation after the second driveoperation.
 10. An image forming apparatus comprising the fixing deviceaccording to claim
 1. 11. A control method of a fixing device thatincludes a first roller, a second roller that is provided in contactwith the first roller, and a cleaning member that is provided in contactwith the second roller to clean the second roller, the membercomprising: driving the first roller to rotate and driving the secondroller swingingly relative to the first roller by a driver; andcontrolling the driver to drive swingingly the second roller relative tothe first roller so as to change a pressure between the second rollerand the first roller and a pressure between the second roller and thecleaning member to a predetermined relationship in accordance with aposition to which the second roller is driven swingingly, wherein thepredetermined relationship according to the position to which the secondroller is driven swingingly in such that when the second roller isdriven swingingly to a first position on a side of the first roller, thepressure between the second roller and the first roller is a firstroller pressure and the pressure between the second roller and thecleaning member is a first cleaning pressure, and when the second rolleris driven swingingly to a second position on a side of the cleaningmember, the pressure between the second roller and the first roller is asecond roller pressure less than the first roller pressure, and thepressure between the second roller and the cleaning member is a secondcleaning pressure larger than the first cleaning pressure.